Messages in this thread Patch in this message | | | Date | Wed, 13 Nov 2013 09:25:22 -0800 | From | tip-bot for Rik van Riel <> | Subject | [tip:sched/urgent] sched/numa: Fix NULL pointer dereference in task_numa_migrate() |
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Commit-ID: 46a73e8a1c1720f7713b5e2df68e9dd272015b5d Gitweb: http://git.kernel.org/tip/46a73e8a1c1720f7713b5e2df68e9dd272015b5d Author: Rik van Riel <riel@redhat.com> AuthorDate: Mon, 11 Nov 2013 19:29:25 -0500 Committer: Ingo Molnar <mingo@kernel.org> CommitDate: Wed, 13 Nov 2013 13:33:51 +0100
sched/numa: Fix NULL pointer dereference in task_numa_migrate()
The cpusets code can split up the scheduler's domain tree into smaller domains. Some of those smaller domains may not cross NUMA nodes at all, leading to a NULL pointer dereference on the per-cpu sd_numa pointer.
Tasks cannot be migrated out of their domain, so the patch also sets p->numa_preferred_nid to whereever they are, to prevent the migration from being retried over and over again.
Reported-by: Prarit Bhargava <prarit@redhat.com> Signed-off-by: Rik van Riel <riel@redhat.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Cc: Mel Gorman <mgorman@suse.de> Link: http://lkml.kernel.org/n/tip-oosqomw0Jput0Jkvoowhrqtu@git.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org> --- kernel/sched/fair.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index df77c60..c11e36f 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -1201,9 +1201,21 @@ static int task_numa_migrate(struct task_struct *p) */ rcu_read_lock(); sd = rcu_dereference(per_cpu(sd_numa, env.src_cpu)); - env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2; + if (sd) + env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2; rcu_read_unlock(); + /* + * Cpusets can break the scheduler domain tree into smaller + * balance domains, some of which do not cross NUMA boundaries. + * Tasks that are "trapped" in such domains cannot be migrated + * elsewhere, so there is no point in (re)trying. + */ + if (unlikely(!sd)) { + p->numa_preferred_nid = cpu_to_node(task_cpu(p)); + return -EINVAL; + } + taskweight = task_weight(p, env.src_nid); groupweight = group_weight(p, env.src_nid); update_numa_stats(&env.src_stats, env.src_nid);
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